In many prior art voice-recognition systems, the operator or speaker must first "log in", manipulate or adjust one or more control knobs or buttons to enter an identification code, or otherwise inform the voice recognizer of who the operator is so that the recognizer can reference the voice templates which were generated when the operator trained the system to his or her voice initially. Since voice recognition systems are often speaker dependent, a set of templates is required for each user. If several users were using the same recognizer system, a set-up code for keyboard entry would be required to specify which user template to be used for the recognition system.
This "logging in" procedure is therefore inefficient since one purpose of voice control of a two-way mobile radio is to alleviate the need to divert a driver's attention from operating the vehicle to manipulate or adjust such knobs on the radio. In addition, this procedure is cumbersome. It forces the operator to remember another number, for example, to identify what car number the operator is in, which batch number he or she has, and which user the operator is. Thus this cumbersome method detracts from the main purpose of using voice control in the first place, which is to improve usability.
There is also another problem in using voice-operated commands or functions to operate a mobile radio in a vehicle. Since normal conversations inherently occur inside vehicles, a VOX-operated transmitter or a voice-controlled radio will (unless deactivated) try to transmit or operate on every word that is detected. For example, a voice command or keyword used accidentally during a conversation could cause an undesired function to be performed by a voice recognition unit.
Earlier developments of voice recognition systems for high noise environments have typically utilized head mounted or hand-held microphones. Such systems have attempted to overcome the problem of background noise by requiring that the microphone be positioned close to the mouth. Although this may be a somewhat effective solution for this type of system, a head mounted or hand-held microphone arrangement is not practical, nor acceptable, for many systems.
For use in a vehicle, the most desirable types of voice recognition systems are those which operate hands-free. A hands-free system is extremely practical in cases where the operator is required to manually handle controls, such as while driving. However, due to the high background noise in such an environment, the speech recognition system must be able to accurately distinguish words from the background noise, and other conversations, as well as free the operator from manual control of a microphone. A system of this kind offers substantial improvement to the operator's productivity and concentration.
Therefore what is needed is a simple method to reduce the percentage of time that an undesired operation (VOX or voice recognition unit) of a voice operated mobile radio is triggered in a high noise or conversation laden environment.